Exhaust gas discharged from a boiler of a power generation facility contains pollutants such as nitrogen oxides (NOx), dust, and sulfur oxides (SOx). Therefore, boiler facilities are equipped with environmental facilities such as a denitration facility for removing nitrogen oxides, an electrostatic precipitator for removing dust, and a desulfurization facility for removing sulfur oxides, in the rear of the combustion chamber.
Recently, as environmental regulations have been strengthened, catalysts have been added to the denitration facility. In the electrostatic precipitator, a bag filter is additionally installed to enhance the collection efficiency by a hybrid method. In addition, in the desulfurization facility, the desulfurization efficiency has been increased by increasing the amount of limestone or increasing the volume of the reactor.
However, since the pressure loss of the boiler increases due to the addition of such environmental facilities, it is necessary to increase the capacity of the boiler blower or lower the load of the boiler. Moreover, since environmental facilities are degraded due to aging, the number of cases where the boiler is operated by lowering the load is increasing in order to comply with environmental regulations.
Recently, as the quality of coal has been lowered, the amount of air supplied to the boiler has been increased to increase the combustion efficiency of coal in the boiler. However, in this case, the amount of exhaust gas is increased, and it is difficult for environmental facilities to cope with the increased amount of exhaust gas. Therefore, there is a case where the load of the boiler is lowered to reduce the amount of exhaust gas.
On the other hand, there is a case where the power generation facility is operated with higher output than the design capacity of the boiler due to power shortage. In this case, damage to the environmental facilities is accelerated, and the boiler may suddenly stop due to damage to main equipment of the environmental facilities. Therefore, it is required to reduce the burden on the environmental facilities by suppressing an increase in the amount of exhaust gas of the boiler.